Paramagnetic nanoparticle T1 and T2 MRI contrast agents

Abstract

There is no doubt that magnetic resonance imaging contrast agents (MRI CAs) can play a vital role in diagnosing diseases. Therefore, demand for new MRI CAs with an enhanced sensitivity and advanced functionalities is very high. Here, paramagnetic nanoparticles (NPs) are reviewed as new potential candidates for either T(1) or T(2) MRI CAs or both. These include surface coated lanthanide (Ln) oxide NPs (Ln = Gd, Dy, and Ho) and manganese oxide NPs. Surface coating materials should be biocompatible and hydrophilic. Compared to conventional large NPs, these surface coated paramagnetic NPs can be made ultrasmall with core particle diameter ranging from 1 to 3 nm, but their magnetic properties are still sufficient for MRI CAs. At this particle diameter, they can be easily excreted from the body through the renal system, which is prerequisite for in vivo applications. Mixed lanthanide oxide NPs into which a fluorescent Ln material is incorporated will be valuable as multiple imaging agents for both MRI-fluorescent imaging (FI) and MRI-cellular imaging (CL). These paramagnetic NPs can be further functionalized towards target-specific imaging, multiplex imaging, and drug delivery.

Functionalized nanomaterials: their use as contrast agents in bioimaging: mono- and multimodal approaches

“…The efficiency of iron oxide probes as T 2 CA is sizedependent and increases with higher particle crystallinity [26,79,86,96,97] . However, these NPs, generally synthesized at low temperatures, have poor crystallinity associated with small size and lack of monodispersity, as also found for the other nanomaterials [98] .…”

“…A way to solve this problem relies in the synthesis of Gdbased paramagnetic NPs [68] , such as Ln 2 O 3 , GdF 3 , and GdPO 4 [26,69,70] , which yield high magnetic moments because of the abundance of paramagnetic ions on their surfaces.…”

Functionalized nanomaterials: their use as contrast agents in bioimaging: mono- and multimodal approaches

“…A way to solve this problem relies in the synthesis of Gd-based paramagnetic NPs, [68] such as Ln 2 O 3 , GdF 3 , and GdPO 4 [26,69,70] which yield high magnetic moments because of the abundance of paramagnetic ions on their surfaces.…”

“…Clinical Imaging modalities generally include complementary techniques [14] such as: optical imaging, [15][16][17][18][19][20][21][22][23] magnetic resonance imaging (MRI), [24][25][26][27] computed tomography (CT), [28] ultrasound imaging (USI) [29][30][31][32][33] positron emission tomography (PET) [34][35][36][37] and single photon emission computed tomography (SPECT) [38][39][40]. Other techniques are also scrutinized, for example multi-photon plasmon resonance microscopy, [41] optical coherence tomography (OCT), [42] surface enhanced Raman spectroscopy (SERS), [15,[43][44][45][46][47] and diffuse optical spectroscopy [48].…”

Gd(III) doping effect on magnetization and water proton relaxivities in ultra small iron oxide nanoparticles

“…5,6 Furthermore, gadolinium oxide nanoparticles have shown r 1 values which are much larger than those of Gd(III)-chelates due to a dense population of Gd(III) ions in a nanoparticle. 7,8 Therefore, it is expected that Gd(III) doping might increase a longitudinal water proton relaxivity (r 1 ) in ultra small iron oxide nanoparticles (high spin doping effect). On the other hand, Gd(III) is known to oppose net magnetic moment of Fe(III)/Fe(II) in oxides, reducing magnetizations (reduced magnetization effect).…”